The research proposed will continue our studies into the action of aqueous radicals on biologically active molecules. The aim of the investigation is to elucidate the chemical phase of radiation action as it contributes to biological manifestations. The following substances will be examined: 1. Amino acids, particularly the ring- and sulfur-containing residues and the basic residues; 2. Peptides containing residues of known reactivity; 3. Chromatin extracted from cultured mammalian cells. The effects of the individual radical intermediates (H, OH, e-aq and O minus 2) will be isolated by irradiating in controlled environments during irradiation. The destruction of amino acids by specific radicals will be determined and a search made for cooperative effects among certain combinations of amino acids and in oligo- and poly-peptides. Chromatin will be studied as a model for the primary molecular effects of radiation on the genetic apparatus in vivo. The effects of radiation on the DNA in chromatin will be measured by strand and base damage and by template activity. Changes in the composition and structure of the chromosomal proteins will be determined, when irradiated separately and when incorporated in the chromatin structure. The effects of radiation on the DNA-protein interaction will be monitored using chemical and enzymatic probes.